1. Field of the Invention
The present invention relates to thermoset polymers and ceramics, and more particularly to silicon and boron-containing thermoset polymers and ceramics.
2. Description of the Related Technology
Thermally stable polymeric elastomers consisting of alternating carborane and siloxane groups are known for both the deca- and penta-carboranes (HCB10H10CH and HCB5H5CH respectively). See, for example, U.S. Pat. No. 3,463,801. Some have been produced commercially. However, these materials do not contain alkynyl moieties such as acetylenic groups or any other functional group for crosslinking to produce thermosetting polymers. These poly (carborane-siloxane) elastomers show superior thermal (high chars) and oxidative properties (low weight loss) at elevated temperatures (900xc2x0 C.) as compared to analogous poly(siloxanes) as monitored by thermogravimetric analysis (TGA).
Silylene or siloxane-acetylene and silylene or siloxane-diacetylene polymers have also been reported. See, for example, U.S. Pat. No. 5,483,017. Good quality fibers can be drawn from the melts of the silylene polymers either thermally or with UV light, but they lack the thermally and oxidatively stable boron-containing units.
Linear inorganic-organic copolymers containing acetylenic and either bis(silyl or siloxyl) carboranyl units or a random distribution of both bis(silyl or siloxyl)carboranyl and bis(sily or siloxy) units have also been described. See, for example, U.S. Pat. No. 5,272,237. However, these polymers contain carborane units in each repeating unit which add to their cost.
Accordingly, it is an objective of certain embodiments of the present invention to provide a thermoset polymer having improved thermal stability by incorporating boron into its backbone.
It is another objective of certain embodiments of the present invention to provide a low cost boron-containing thermoset polymer.
In a first aspect, the present invention provides a thermoset polymer produced by reacting a first compound having at least one alkynyl group, at least one silyl group and/or at least one siloxyl group, with a second compound selected from boric acid, hydrocarbon boronic acid, hydrocarbon borate, and pyroboric acid under reaction conditions sufficient to crosslink a sufficient number of alkyne bonds to produce a thermoset polymer.
In a second aspect, the present invention provides a method of preparing a thermoset polymer including the step of reacting a first compound having at least one alkynyl group, at least one silyl group and/or at least one siloxyl group, with a second compound selected from boric acid, hydrocarbon boronic acid, hydrocarbon borate, and pyroboric acid under reaction conditions sufficient to crosslink a sufficient number of alkyne bonds to produce a thermoset polymer.
In a third aspect, the present invention provides a thermoset polymer having a repeating unit comprising at least one crosslinking group having at least one unsaturated carbon-carbon bond and at least two bonds that form crosslinks between polymer chains, at least one borate group, at least one silyl group and/or at least one siloxyl group.
In a fourth aspect, the present invention provides a ceramic material produced by pyrolyzing a combination of a first compound having at least one alkynyl group, at least one silyl group and/or at least one siloxyl group and a second compound selected from boric acid, hydrocarbon boronic acid, hydrocarbon borate, and pyroboric acid; or by pyrolyzing a polymeric composition reaction product of a combination of the first and second compounds.